DE2736424A1 - LIQUID CRYSTAL MATERIAL AND ELECTRO-OPTIC LIQUID CRYSTAL DISPLAY DEVICES THEREFORE - Google Patents

Description

The invention relates to diphenylcarboxylic acid esters which form liquid-crystalline phases, and to electro-optical display devices which contain these materials.

Certain organic compounds form liquid-crystalline phases, which are an intermediate state between the crystalline solid on the one hand and the completely disordered liquid phase on the other represent, with an order taking place over wide areas within the liquid-crystalline area of the molecules takes place.

293- (JX / 5038/04) -FSBk

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The two main types of liquid-crystalline phases are the smectic mesophase, in which the over wide areas is of the substantially lamellar type, as well as the nematic mesophase in which the Order is essentially linear, so the molecules tend to move with their long axes align parallel to each other. This is also sometimes referred to as a subclass of the nematic mesophase the cholesteric mesophase, which is sometimes referred to as a separate mesophase. Latter possesses a helical long-range order which is superimposed on the linear arrangement in the nematic mesophase. Compounds that have a cholesteric mesophase are optically active (chiral), the The slope of the helices depends on the type of molecule and the extent of the optical activity. The slope the helices can be such that thin layers of the Chulesterin phase reflect visible light, which leads to light colors being observed; the slope can also be sharply dependent on temperature, which means that certain colors are reflected over certain temperature ranges, so that the Respective cholesteric mesophase can be used as a kind of thermometer. The underlying phenomenon is known as so-called thermochromism.

The invention relates to liquid crystal materials, which consist of esters of the following general formula:

CH ₃ CH ₂ CH (CH ₃ ) (CH ₂ ) _n - ^ V / Q \ _ _C0 q-

where η is an integer from 1 to 3 and R is a straight or branched C ₁ - to C ₁₀ -alkyl group, which is also a

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can have chloral center, mean.

The alkyl group R is preferably straight-chain and contains 4 to 10 carbon atoms.

Due to their molecular structure and optical activity, the compounds according to the invention have a cholesteric mesophase (hereinafter referred to as Ch) and a chiral smectic C mesophase (hereinafter briefly referred to as S_), which is the cholesteric Mesophase superimposed. The compounds according to the invention show both by themselves and in admixture with one or

several suitable for the formation of S ^ liquid crystal phases

th compounds form a chiral S_ liquid crystal phase in which the molecules are arranged obliquely in the smectic layers, which in turn are superimposed on one another in such a way that a helical distribution of the tilt angles is present when passing through a number of such layers. The chiral S _c phases of the compounds according to the invention also have the extraordinary property that

the mesophases in their planar S_ textures form a helix

have generation that leads to a selective reflection of colored light of certain wavelengths, which is temperature-dependent is, which means that the compounds of the invention exhibit thermochromism.

In addition to the above-mentioned S _c -Ch transition, the compounds according to the invention, both alone and in a mixture with one or more other liquid crystal compounds, show a cholesteric liquid crystal phase in which the molecules are arranged in the helix arrangement of this phase in such a way that a layer of this phase in the Grandjean plane texture, the plane of polarization of incident polarized light rotates and elliptically

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polarized light of certain wavelengths is reflected when irradiated with ordinary light, whereby the corresponding mesophases also show thermochromism.

The compounds of the invention have properties that make them suitable for use in electro-optical Make liquid crystal display devices suitable, for example in devices based on phase changes, in which the material is between a so-called 'focal conical' cholesteric state that scatters light, and changes to a transparent nematicη state, when an electric field is applied; According to a first aspect of the invention, an electro-optical display device according to the invention contains one of the compounds defined above as liquid crystal material. It is furthermore also possible that a mixture or a solution of the abovementioned compounds is also present can and also that other compounds with liquid-crystalline behavior are present. The mixture of the compounds used is preferably a eutectic mixture. The optical effectiveness of the electro-optical display devices can be increased by using pleochroic dyes. For this Purpose-suitable pleochroic dyes are, for example, in GB patent applications 25843/75 and 25859/75 described.

According to a second aspect of the invention, the inventive electro-optical display device contains as

Liquid crystal material has an ohiral wide range S_ phase

from a mixture or a solution of the inventions defined above in such a way that the selectively light-reflecting (ie colored) chiral S _c phase by an applied

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electric field is converted into a light non-reflective homeotropic (colorless) phase. This means, that the slope of the planar S structure is effectively wound up by an external electric field, which changes the tilted orientation of the molecules so that they eventually have an orthogonal orientation relative to each other of the layers.

The compounds according to the invention have both a chiral S _c phase and a Ch phase at higher temperatures, mixtures of such materials being able to show thermochromism in both mesophases. For this purpose, it is assumed that these properties occur because the helix gradients ier molecular arrangements are such that there is a strongly temperature-dependent Bragg reflection of certain light wavelengths in the visible spectral range. This means that the materials according to the invention appear colored in a color which depends on the temperature of the material. The sequence of the resulting colors when the temperature changes in one direction in the case of the cholesteric phase is the opposite of the sequence in the case of the chiral S ^ phase. The materials according to the invention and their mixtures or solutions can be used accordingly in surface thermography, for example for diagnosing breast cancer.

The latter property can also be used in the manufacture of temperature sensitive display devices can be used, for example, for the production of thermometers with visual display, which on the influence of temperature based on the helix pitch of the material.

The invention is illustrated below by means of examples

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- fr -

explained, which relate to typical synthetic routes for the preparation of the compounds according to the invention.

The following abbreviations are used:

(+): optically active material with a positive optical rotation angle

(-): optically active material with a negative optical rotation angle

: absolute measure of the optical rotation (specific rotation) of an optically active material in 10% solution (weight / volume) in chloroform.

Example 1:

Preparation of (+) - 4- (2 "-Methylbutyl) -diphenyl-V carboxylic acid

The preparation of (+) - 4- (2 "-Methylbutyl) -diphenyl-V carboxylic acid happens in the following reaction path:

Level Bl

Stage Cl

- (OMO / " ⁰¹ "

Level Dl

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2736A24

(+) CH, CH ₂ CH (CH

OOH

Grade Al; Manufacture of Dighenxl2l-4-magnesium broniid

Procedure ^

(+) - 2-Methylbutyl bromide (0.07 mol) (prepared in Step A3 of Example 3) in dry tetrahydrofuran
(20 ml) turns into magnesium turnings (0.2 g-atom) in
dry tetrahydrofuran (20 ml) was added and the mixture was stirred for 0.5 h. The reaction will go through
dropwise addition of the alkyl bromide kept under control.

Then 4-bromodiphenyl (0.13 mol) in dry Tetrahydrofuran (20 ml) was added dropwise so that there was constant reflux of the solvent. When the addition is complete, the reaction mixture is stirred and refluxed for 4 h, after which it is overnight is left standing.

Level Bl;

The solution of the Grignard reagent prepared in step A1 is cooled in an ice bath, followed by a solution of ferric chloride (0.005 mol) in dry tetrahydrofuran (1.5 ml) is added dropwise with vigorous stirring; then a solution of (+) - 2-methylbutyl bromide (0.2 mol) in dry tetrahydro-

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furan (20 ml) added. The mixture is stirred for 12 hours and then refluxed with stirring for 12 h. After cooling, the mixture is poured into a jar with ice (200 g), water (400 ml) and concentrated hydrochloric acid (40 ml) poured in and stirred for 0.5 h.

The aqueous mixture is then extracted with ether (4 × 200 ml), after which the combined extracts are washed with water (3 × 100 ml) and then dried over anhydrous sodium sulfate. After evaporation of the solvent, the oily crude product (40 6o ⁰ C Kp.) Is purified using a silica gel column, eluting with petroleum ether. The purified product is then distilled at 0.1 torr.

Stage Cl: Preparation of _ (+ 2 _z 4 _Z- (2 ^ _:: MethYlbut2l]; V-bromo _r diphenyl

A solution of bromine (0.5 ml) in dry chloroform (5 ml) is added to the (+) - 4- (2'-methylbutyl) -diphenyl (0, 04 mol) was added under anhydrous conditions. The reaction mixture is during the reaction time on 0 ⁰ C j
will.

0 ⁰ C kept, with the reaction vessel protected from light

After 18 and 36 h, two further amounts (2 × 4 ml) of the bromine solution in chloroform (10 volumes #) are added.

18 hours after the second addition, the mixture is poured into a sodium metabisulphite solution (150 ml). The aqueous solution is extracted with ether (3 × 8θ ml). The combined extracts are washed with water (3 × 50 ml) and dried over anhydrous sodium sulfate.

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net, whereupon the solvent is evaporated. The crude solid is made from ethanol to constant melting point recrystallized.

Level Dl:

c ^ anodighenjl

This reaction, which is a conventional organic synthesis reaction, is carried out analogously to step P2 of the Example 2 below carried out.

Level El:

ii 1 z

The preparation of (+) - 4- (2 "-Methylbutyl) -diphenyl-4'-carboxylic acid from the corresponding nitrile can be done as follows:

(+) - 4- (2 ^M -methylbutyl) -4'-cyanodlphenyl (0.015 mol) as obtained in step Dl is dissolved in methanol (50 ml) and added to a mixture of potassium hydroxide (0.54 mol) and sodium hydroxide (0 , 75 mol) in methanol (40 ml) and water (20 ml) were added. The solution is then refluxed until the evolution of ammonia ceases, which takes about 72 hours. The mixture is then diluted with water (1000 ml) and acidified with concentrated hydrochloric acid. The precipitated product is filtered off and crystallized twice from ethanol.

Transition temperatures:

Crystal cholesteric liquid crystal: 224 ° C;

cholesteric liquid crystal - isotropic liquid: 247.4 ⁰ C.

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V-

Example 2;

Preparation of (+) - 4- (3 "-methylpentyl) -4'-carboxylic acid

The manufacture of (+) - 4- (5 "-Methylpentyl) -4'-carbon acid happens in the following reaction path:

(-JCH ₃ CH ₂ -CH (CH ₃ ) CH ₂ OH ^{level A2} )

(+) CH ₃ CH ₂ CH (CH ₃ ) CH ₂ COCl g ^{stage C2} (+ stage D2

( ₊ ) cH ₃ cH ₂ cH (cH ₃ ) cH ₂ c '- \ Or \ Oy ~ ^Br

JCH ₃ CH ₂ CH (CH ₃ JCH ₂ CH ₂ ~ (O

(+) CH, CH ₀ CH (CH,) CH ₀ CH

Level B2

Level E2

Level G2

^00H *

Level A2;

Phosphorus tribromide (0.135 mol) is added dropwise with stirring to a solution of commercially available (-) - 2-methylbutanol (0.14 mol) in dry pyridine ('Analar', (0.12 mol)) The addition is kept by cooling the mixture in an ice bath below 15 ^° C. The white emulsion formed

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is stirred for 2 h at room temperature. The crude bromide is then extracted from the emulsion under reduced pressure (300 torr) distilled off until the mixture takes on an orange ^ red color and 'boils'.

The crude distillate is then taken up in petroleum ether (boiling point 4o / 6o ⁰ C; 100 ml) and washed with:

(a) 5 # sodium hydroxide solution (3 x 50 ml),

(b) water (3 χ 50 ml),

(c) 10 # sulfuric acid (2 χ 50 ml),

(d) concentrated sulfuric acid (100 ml) and

(e) water (2 100 ml).

After drying the solution over anhydrous sodium sulfate, the solvent is evaporated. The residue is distilled; the fraction boiling at 121 ^° C. is obtained (96.5 % purity according to GLC). [λ] ^ ⁰ 3.9 °.

Level B2; Production_of _ ^ + | -3; {jethjlgentansäure

Under anhydrous reaction conditions, the (+) - 2-methylbutyl bromide prepared in step A2 becomes (0.38 mol) prepared the Grignard reagent in a conventional manner. The freshly made reagent is on crushed solid dry ice (450 g) poured into ether and the mixture stirred until a paste was formed will. The slurry is acidified with 50 # aqueous hydrochloric acid (24o ml). The ether layer and the ether extracts the aqueous layer with 25 ^ iger sodium hydroxide solution (3 × 60 ml) extracted. The sodium hydroxide extracts are then mixed with concentrated hydrochloric acid acidified and then quenched with ether (4 χ 100 ml)

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shakes. The ether extracts are washed with water (2 × 50 ml) and dried over anhydrous sodium sulfate, after which the solvent is evaporated. The residue is distilled under a slight vacuum (450 Torr), the fraction boiling at 136 ⁰ C fraction is recovered; [x] ^ ⁰ 6.4 °,

Stage C2: Production of _ {+) 33; Methjlgentano2lchlorid

The acid obtained in Step B2 is purified using thionyl chloride according to a conventional method in converted the corresponding acid chloride. After removing excess thionyl chloride, the remaining Acid chloride used in stage D2 without further purification.

Stage D2: Production_of _ (+) _:: 4 _r {3 ^ _:: MethYlgentano2l} _r V _r bromdigheny_l

To a mixture of anhydrous aluminum triochloride (0.1 mol) and dry dichloromethane (40 ml) is added dropwise a mixture of 4-bromodiphenyl (0.086 mol) and (+) - 3-methylpentanoyl chloride (0.1 mol) in dichloromethane (80 ml ) admitted. The mixture is then stirred for 18 hours. The mixture is then poured into a beaker with ice (100 g), water (30 ml) and concentrated hydrochloric acid (50 ml) and stirred for 0.5 h. The organic layer is then separated off, washed with water (2 × 40 ml) and dried over anhydrous sodium sulfate, after which the solvent is evaporated off. The crude product is then crystallized from ethanol up to a constant melting point; F. 97 ⁰ C.

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Level E2; Production_of_X +) _r 4 _I [3 ^ ₌ Methxlßent2l} ₌ V _r bromdighen ^ l

To lithium alanate (0.063 mol) in sodium dried Ether (100 ml) are added:

(a) anhydrous aluminum trichloride (0.135 mol)

in ether dried with sodium (100 ml) as well

(b) (+) - 4- (3 "-Methylpentanoyl) -44> romdiphenyl (0.0185 mol) in dry chloroform (200 ml) at a rate such that the mixture slowly boils.

The reaction mixture is then kept at the boil for 18 h with stirring. After that, excess lithium alanate is used destroyed by careful addition of water to the mixture.

The mixture is then poured into a solution of ice (200 g), water (60 ml) and concentrated hydrochloric acid (100 ml) and stirred for 0.5 h.

The organic layer is separated, washed with water (3 × 100 ml) and dried over anhydrous sodium sulfate, after which the ether is evaporated. The solid product is recrystallized from ethanol to a constant melting point; F. 101-102 ⁰ C.

Level F2:

A mixture of (+) - 4- (3 "-methylpentyl-4'-bromodiphenyl (0.03 mol, product of stage E2), copper (I) cyanide (0.03 mol)

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and N-methylpyrrolidone (38 ml) is refluxed with stirring for 2 hours. The cooled reaction mixture is then poured into a solution of iron (III) chloride (12 g), concentrated hydrochloric acid (5 ml) and water (150 ml) and ^{stirred at 60 °} C. for 0.5 h.

The organic material is then taken up in fither; the extract is diluted with Hydrochloric acid (2 × 100 ml) and water (3 × 100 ml) and dried over anhydrous sodium sulfate, after which the solvent is evaporated.

The crude oily product is then purified by column chromatography using a silica gel column and chloroform as an eluent. The purified product is distilled out at 0.1 torr and an oil bath temperature of I80 C ^0.

Stage G2: Production_of _ {+} ₌ 4 _: £ 2 ^ ₌ MethxlBentjl2 _: dlBhenj [l ₌

The preparation of (+) - 4- (3 "-Methylpentyl) -diphenyl-4'-carboxylic acid is made from the corresponding nitrile. The acid can analogously to the process of stage E1 in example 1 manufactured and cleaned.

The colorless crystals have the following transition temperatures:

Crystal cholesteric liquid crystal: 219 ° C

cholesterol liquid crystal - isotropic liquid: 242.2 ⁰ C.

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Example 3:

Production of (+) ~ 4- (4 ^tl -Methylhexyl) -dlphenyl-4 ^t carboxylic acid

The production of (3) -4- (4 ⁿ -Methylhexyl) -diphenyl-4 · -carboxylic acid takes place in the following reaction path:

(+) CH ₃ CH ₂ CH (CH ₃ ) CH ₂ Br

Level A3

(+ JCH ₃ CH ₂ CH (CH ₃ ) (CH ₂ J ₂ COCl

CH (OT J (CH ₂

(+ JCH ₃ CH ₂ CH (CH ₃ ) (CH ₂ J ₃ _ / QWq \ _ _cn

step

(+ JCH ₃ CH ₂ CH (CH ₃ J (CH ₂ J ₃ ~ \ O

JOOH

Stage A3: Production of _ {+) - 4-Methjrlhexanoic acid

(+) - 2-Methylbutyl bromide prepared as in step A2 of Example 2 is converted into (+ J-4-methylhexanoic acid) by reaction with diethyl malonate and subsequent hydrolysis of the ester using a process known from the literature. The product (96 % purity according to GLC) boils 134 ° C / 25 torr.

f 9. »° ·

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Stage b4; Production_of _ {+} - 4 _:: Meth2lhexanoxlchlorid

The acid of stage A3 is made by reacting Thionyl chloride converted to acid chloride by a conventional method. Excess after removal Thionyl chloride, the remaining acid chloride is used in stage C3 without further purification.

Level C3; Production_of_j [+2 _:: 4 _:: (42-Meth2lhexanoYl} _z 4 ^ - bromdighenjl

The acid chloride from stage B3 is reacted with 4-bromodiphenyl according to the process described in stage D2 of Example 2. The product obtained is recrystallized from ethanol to a constant melting point; P. 56 ⁰ C.

The product shows a monotropic smectic phase when the isotropic liquid cools below the melting point to 28 ^° C.

Level D3; Production_of _ (+ 2 ₌ 4 ₌ (42 ₌ Methxlhex2l) ₌ V ₌ bromdighen ^ l

The compound is prepared by a reduction process analogous to step E2 of Example 2. The solid product is recrystallized from ethanol to a constant melting point, F. 86 - 89 ^° C.

Level E3; Production_of _ (+} _I 4 _I {4 || _:: Methj; lhexYl2 _I V _: -c2ano _r dighengl

The connection is made in the same way as the procedure in stage F2 from Example 2 and purified.

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Level F3:

The preparation of (+) - 4- (4 "-methylhexyl) -diphenyl-4'-carboxylic acid is made from the corresponding nitrile.

The reaction, like the purification of the product, can be carried out analogously to the process of step E1 of example 1 a material with the following physical properties is obtained:

Transition temperatures:

C-Sc 175.4 ° C, Sc-Ch: 219.1 ⁰ C and Ch-I: 235.8 ⁰ C.

Example 4; Production of 4-alkoxyphenols

The production of 4-alkoxyphenols takes place in the following reaction path:

where R is an alkyl group such as an n-alkyl group means.

Level A4; Manufacture_yon_4-Alkoxy ^ henolem

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SO

A solution of potassium hydroxide (2.15 mol) in water (238 ml) is added over 30 min to a refluxed mixture of p-quinone (2 mol) and 1-bromooctane (2.3 mol) in ethanol (640 ml) added. After heating for a further k h, the cooled and diluted mixture is extracted by shaking with ether (500 ml), after which the aqueous phase is acidified. After cooling, this is extracted with chloroform (4 × 500 ml), whereupon the combined extracts are washed with water (3 × 200 ml). After drying over sodium sulfate, the chloroform solution is evaporated and the remaining residue is chromatographed on silica gel using chloroform as the eluent. The combined Monoatherfraktionen be from hexane umkristallisiertj F. 63 ⁰ C.

The other 4-alkoxyphenols can be used analogously Reactions are prepared starting from the corresponding 1-bromoalkanes.

Example 5; Production of diphenyl-4'-carboxylic acid esters

Diphenyl-4 ¹ -carboxylic acid esters according to the invention are prepared by the following reaction route:

COOH

Level B.

0 - <Or ^0R *

( ₊ ) a / oV (O

where A and R are as defined above.

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Stage A5: Production of _ {+ 2; 4-Alk2ldighenyl ₌ 4 ^ -carboxylic acid chlorides

The preparation of (+) - 4-alkyldiphenyl-4'-carboxylic acid chlorides is explained using the example of the preparation of (+) - 4- (2 ^M -methylbutyl) -diphenyl-4'-carboxylic acid chloride.

(+) - 4- (2 "-Methylbutyl) -dipheny1-4'-carboxylic acid prepared as in step E1 in Example 1 (0.002 mol) is mixed with thionyl chloride (20 ml) under anhydrous conditions Heated for 1.5 h. Excess thionyl chloride is then separated off by distillation under reduced pressure. The remaining acid chloride is used in the next following stage without further purification.

Stage B5: Production_of_j [+} _:: 4 _:: {2 " _:: MethYlbutxl} -di2henYl _:

The ester production is based on the synthesis of (+) - 4- (2 "-methylbutyl) -dlphenyl-4'-carboxylic acid n-heptyloxyphenyl ester explained.

(+) - 4- (2 "-Methylbutyl) -diphenyl-4 ¹ -carboxylic acid chloride (0.002 mol) prepared in ^{step A5 is dissolved in dry pyridine ('Analar 1} , 10 ml) and cooled in an ice bath step A4 of example 4 produced 4-n-Heptyloxyphenol (0.002 mol) was added to the above solution with stirring, and the mixture 18 h is stirred under heating let to room temperature. the mixture is then heated for 1 h at 100 ⁰ C. Thereafter, the Separated pyridine in a rotary evaporator and the residue by column chromatography on silica gel using chloroform as the eluent.

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cleans. The combined ester fractions are recrystallized from hexane.

Analogous esters can be used in an analogous manner of reaction using the corresponding carboxylic acids and Phenols are made from raw materials.

In Table 1 below are physical properties for a number of those made in this manner Ester stated:

Table 1

Constants for some connections of the general

structure

(+) CH ₃ CH ₂ CH (CH ₃ ) (CH ₂ ) _n -

ρ C-So or SC - Ch Ch - I Δ Η, __ Ch ( ⁰ C) ( ⁰ C) ( ⁰ C) (kcal-mol- ¹ )

η = 1;

nC ₄ H ₉ 81.7-169.3 5.3

11-C ₅ H ₁₁ 79.8 (70) 164.5 6.9

nc ₆ H ₁₃ 68.8 80.2 16 ^ .5 5.3

ⁿ " ^C 7 ^H 15 ^8o ' ^{4 87} ' ^{3 157} ' ^{5 7} ' ² nc ₈ H ₁₇ 76.6 88.6 155.4 10.7 HC ₉ H ₁₉ 79.3 89.5 1 * 7.6 10 , 2 nC ₁₀ H ₂₁ 73.5 90.5 146.4 10.5

ⁿ " ^C 6 ^H 13 ⁸¹ '° 120.3 120.3

The following abbreviations are used:

C - S _c or Ch: transition temperature from crystalline

too chiral smectic C or cholesteric,

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- Si -

S _c - Ch: transition temperature from chlral smectic C to cholesteric,

Ch - I: transition temperature from cholesteric too isotropic liquid,

Δη: total melting enthalpy for the transition of the stable crystal (C) to the liquid crystalline phase S or Ch,

(): Brackets around temperatures indicate

a monotropic transition that does not occur with a heating cycle, but with cooling is observed, which is accordingly a monotropic transition.

The racemic analogs of all listed in Table 1 Optically active materials can by the same procedure as indicated above using the appropriate racemic reactants can be prepared as starting materials.

It can be seen from the data in Table 1 that none of the pure materials listed are liquid-crystalline Phase at sufficiently low temperature to direct for applications, for example at room temperature Interest to be. However, the compounds are of interest in that they can be used as ingredients in the mixture Production of eutectic mixtures with einaad · ©. » or with others Compatible, liquid-crystal-forming materials are suitable, since the mixtures or solutions are then considerably lower Temperatures show a cholesteric and / or a chiral S ^ phase.

In this context it is also worth mentioning that the chiral S _c phase and the Ch phase of each of the individual compounds always have the same direction of rotation (right or left screw) of their helices. Connections with odd

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^ l

Numerous η in the grouping CH ₃ CH ₂ CH (CH ₃ ) (CH ₂ / -, which have the absolute S configuration, have right-hand screws in their helices, while those compounds in which η «» is an even number in the S _N- and Ch-phases have left-handed screws.

Two exemplary mixtures are given below, the color change temperatures of which are also given are.

Mixture 1:

Components Molenbruch (%)

(OVco 0- / O) - ° ^c 4 ^H 9 " ⁿ ° ' ⁴ °

A - / OV \ O / - ^co 0- / OV OC ₅ H ₁ jn 0.31

A - / OV / OVCO O - (O ^ - OC _? H ₁₅ -n 0.29

where A is (+ JCH ₃ CH ₂ CH (CH ₅ ) CH ₂ -.

Transition temperatures ( ⁰ C): C - S _c : ^ 9

S _c - Ch: 12 Ch - I: 163.3

When looking at a thin layer the planar texture of this mixture is perpendicular to the layer and the colors observed in reflection are:

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Selective reflection Temperature (C)

blue 50.0 turquoise 57.0 green 59.0 yellow 66.5 orange 67.2 Red 68.5

Transition to the low cholesterol state (S _c -Ch):

Red

yellow

green

turquoise

Blue 72.0

72.5 72.8 74.0 83.0 84.5

Selective reflection:

Transition to isotropic liquid 92.0 163.3

Mixture 2:

Components

Breakwater (%)

0C "H ₉ -n

0.24

0.16

0.32

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96

Continuation, mixture 2: Components

Mole fraction {%) 0.15 0.07

0.06

Transition temperatures ( ⁰ C): C - S _c : 39.4

S _c -Ch: 74.5 Ch-I: 162.2.

When looking at a thin layer the planar texture of this mixture is perpendicular to the layer and the colors observed in reflection are:

Selective reflection

Red

yellow

green

turquoise

blue

turquoise

green

yellow

Red

Temperature (° c)

39.0 41.0 43.0 43.4 43.7 58.7 6o, o 67.0 69.0

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- a $ - Components 2736424 3.1 to the cholesteric State (S-Ch): Breakwater ($) Red yellow 7, 3 green 74.5 turquoise 74.8 blue 77 Blue / purple 85 90 97

Transition to isotropic liquid 162.2.

The color changes within the temperature range

9 - '
Spectrum.

from 59 - 4 ^, 7 ° C results in a rather narrow rainbow

The racemic analogs of the optically active esters mentioned above can also be used as components of eutectic Mixtures are used, creating a valuable additional opportunity to change the slope the chiral phase and thus also the color is accessible, which is achieved without changing the composition of the mixture will.

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ORIGINAL INSPECTED

Claims (8)

Expectations Liquid crystal material of the general formula CH ₃ CH ₂ CH (CH where mean: R is a straight-chain or branched C, - to C, _Q -alkyl group, which can also contain a chiral center, and η the numerical values 1, 2 or 3. 2. Liquid crystal material according to claim 1, characterized in that R is a straight-chain C ^ - to C _l0 -alkyl group. 3. Liquid crystal material according to claim 1 or 2, characterized in that η - 1 is. 4. Electro-optical liquid crystal display device of the phase change type, characterized in that it is an ester naoh one of the liquid crystal material Claims 1 to 3 or a mixture or a solution of these esters or one or more of these esters with other liquid crystal materials. 5. Device naoh claim 4, characterized in that that the mixture of liquid crystal materials is a eutectic mixture. • 09107/0141 ORlGfNAL INSPECTED ■ yf - 6. Apparatus according to claim 4 or 5 »characterized in that that the liquid crystal material also has a Contains pleochroic dye. 7. A method for surface thermography, characterized in that that a thin layer of an ester or a mixture of esters according to any one of claims 1 to 3 is applied to a surface and the color of the layer is observed in reflection at right angles to the surface will. 8. Use of the liquid crystal materials according to one of claims 1 to 3 in processes for surface thermography as well as for the manufacture of Tvoi ^ FTQsig crystal display devices. 809807/0848